It is often necessary to occlude a defect or an aperture within a body surface, such as a wall or membrane separating cavities within the body. A typical example is a congenital heart lesion called an atrial septal defect. This is a hole, between the two upper chambers of the heart, which must be closed.
King et al., U.S. Pat. No. 3,874,388, and Blake, U.S. Pat. No. 4,007,743 disclose a stainless steel apparatus for closing a shunt in the vascular system. The dual umbrella apparatus has six ribs which retain the umbrella in an open position. The King et al. apparatus has "barbs" at the ends of the ribs anchor onto the tissue surrounding the shunt. Alternatively, the barbs on the ribs of one umbrella may insert into holes on the ribs of the second umbrella, see FIG. 15A. The Blake apparatus has pivotally mounted struts which provide a flat surface to which a disk may be secured.
In "A New Percutaneous Vena Cava Filter", Cragg et al. disclose a filter composed of nitinol which when inserted into the inferior vena cava, traps emboli and clots. In the process of placing the filter, there is the threat of dislodging thrombi when the catheter or guide wire is advanced too far.
Lock et al., in Circulation, disclose a spring-loaded clamshell occluder of several sizes. The tension in the arms is manually controlled during delivery such that the arms of the distal umbrella, the one inserted first, are everted during placement, creating a cone.
The Rashkind occluder has two polyurethane foam disks mounted on surgical steel wire assemblies. The occluder is used to seal off the ductus arteriosus and is disclosed in Circulation. Vol. 75., page 583, American Journal of Cardiology, Vol. 64, page 218, and Circulation, Vol. 77, page 1068.
Devices currently used to occlude septal defects, including those indicated above, have been known to dislodge and embolize.